A French curve is designed to create curves that cannot be constructed with a compass. To use a French curve, plot points that are known to lie on the curve and fit the instrument to the points.
![](https://engineeringtechnology.org/wp-content/uploads/2023/05/leaafspring-1024x347-1.jpg)
French curves are available in a wide variety of shapes and sizes. They typically only fit a short section of the curve.
![](https://engineeringtechnology.org/wp-content/uploads/2023/05/frenchCurve1-1024x430-1.jpg)
Flexible rules are available for the same purpose, but they do not produce as good results as French curves.